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April 8, 2011

NOT MY USUAL FARE (revised 4/23): Generally I’ve been sticking to reviewing electronics as it’s easier to provide objective measurements and directly compare performance. I happened to give the Beyerdynamic DT 770 Pro 80 headphones a listen at a dealer and liked them enough to bring them home. They turned out to be an interesting example of how different sources can significantly change headphone sound.

REVIEW UPDATE 4/23: After living with the DT 770 Pros for another few weeks, and having a new “reference headphone” to compare them against, I’ve revised several of my comments in this review. I’ve also incorporated feedback from others. As happens with subjective reviews, it’s easy to let some aspects of a product (such as being really comfortable) bias or mask your subjective opinions of other aspects of the product. Motivation to write a long review comes easier when you’re enthusiastic having just listened to something new—hence all the reviews published soon after a product’s purchase. But it’s more realistic to live with gear long enough for the “newness” to wear off. And, in hindsight, that’s what I should have done here.

WHO’s BEYER? Beyerdynamic is the other popular German headphone company. They’re not nearly as well known among consumers as Sennheiser but they still have a loyal following—especially among musicians and professionals. AKG used to be almost German (Austrian) but is now a Harman International USA brand.

CIRCUM WHAT? The DT 770 is a true circumaural headphone. That’s a fancy way of saying they completely cover the ears. Anything resembling a full size headphone is often lumped into this category, but many still rest at least partly on the ears rather than over them. A good example is the popular Sony MDR-V6 (MDR-7506). They have shallow ear pads and rest mostly against your ears rather than your head. The Beyers pretty much leave my ears alone.

THE BASICS: The DT 770 Pro 80s are surprisingly lightweight (about 9 ounces) full sized headphones intended mainly for studio use. But they’ve also found a loyal following among some home listeners. The rated impedance is 80 ohms and they have an “SPL” rating of 96 dB SPL. Those two numbers mean they’re a bit marginal for use with most portable players (see Headphone Impedance). There is a better DT770 version for portable use. More on that later.

CLOSED MINDED: Full size circumaural cans come in two distinct flavors—open and closed. Most of the best sounding headphones are open to varying degrees. This allows the driver to be less affected by whatever is behind it. At least in theory, open back headphones have fewer reflections and resonances to color the sound. The downside is they let the music leak out which might disturb others. They also let more outside sound in. For some, however, closed cans have practical advantages.

ISOLATIONIST TENDENCIES: Most closed full size headphones don’t isolate as much as some might expect. They’re significantly better than open backed headphones but the best sounding and most comfortable closed headphones tend to have less isolation for some good reasons. For one, they don’t “clamp” the head tightly. While this greatly improves comfort it also lets more noise in. And they usually design the ear pads to intentionally “leak” as this helps vent the chamber between the transducer and the ear for more accurate sound. The ones that act like hearing protection muffs sound significantly worse. The special “M” high isolation version of the DT 770 is a good example—they don’t get good reviews for sound quality and are not as comfortable. If you want both great sound and high isolation, in ear monitors (IEMs) such as those from Shure and Etymotic are the best option. But they have their own downsides.

WHY THE DT 770? I need to listen to headphones for extended periods while not bothering others. And I’m often looking to filter out annoying background noise. With closed back headphones you don’t have to crank up the volume as high to drown out other sounds. That helps save your hearing and also makes for less listening fatigue over the long haul. Serious comfort is a must for listening hours at a time. I have several IEMs, and they’re great for flights, the gym, etc. But my ear canals get sore with long and frequent IEM use. They’re also a hassle to take in and out to talk to others, answer the phone, etc. So that leaves full size circumaural closed cans—like the DT770s. And if you want good sound and genuine comfort, the list is fairly short.

SOME COMPETITION (updated 4/10): The DT 770, with a $200 street price, has some significant competition. The ones I’ve heard are:

Sennheiser HD 280 Pro – You see these recommended everywhere. They’re reasonably priced with a street price around $100. They’re nicely made, fold up, and provide more isolation than many closed headphones. But, like many closed cans, they don’t really sound very good. The also have high clamping pressure, and the ear pads/ear cups are not really big enough to fully enclose most adult size ears without putting pressure on the ear itself. So many, me included, find them rather uncomfortable for long term regular wear. I own the HD280 and I’ll comment more on the sound quality later. They’re 64 ohms and work OK with some portable gear. Sennheiser doesn’t provide a typical sensitivity rating which makes directly comparing their efficiency to other manufactures difficult.

Denon AH-D2000 – I own these and have spent a lot of time with them. For a closed headphone they’re relatively accurate and neutral sounding. They’re more comfortable than the HD280 but they’re relatively heavy and have oddly shaped ear pads that, despite being very soft and well made, put some pressure on the ears that gets annoying after a while. They also have a relatively stiff cloth covered cord that doesn’t stay out of the way very well. They’re 25 ohms with a very efficient 106 dB sensitivity rating so they work with portable gear but readily reveal flaws in a portable player or lossy MP3 track. They’re also nearly twice the street price of the DT 770s at around $350.

Audio-Technica ATH-M50 – Like the Beyer DT 770 Pros, these $150 cans are designed for studio use. They have a fairly loyal following and I think sound much better than the HD280s above. The bad news is they suffer from what I call “Shallow Ear Cup Syndrome” . There’s almost no “depth” to the inside of the ear cup once the earpads compress against your head and this leaves the ear itself squished up against a thinly padded area that protects the driver. They also clamp with enough pressure to bother many people after a while. If you don’t need to wear them for long periods, or have tough ears, they’re worth checking out. I had a pair of these for a short time and discuss their sound later. They also have a relatively low impedance at 38 ohms and high sensitivity of 99 dB making them a decent match for portable listening without using an amp.

Sony MDR-V6 (and the very similar MDR-7506) – These are the cheapest of everything here—about $80 street price. And they sound better than the HD280s But they suffer from Shallow Ear Cup Syndrome worse than the M50s above and sound artificially bright. Some suggest different earpads help make them more comfortable. I own a pair and never use them anymore because I can’t stand to wear them for more than an hour or so. They’re rated at 63 ohms and 106 dB sensitivity and work reasonably well with portable gear.

DT 770 CONFUSION: Beyerdynamic’s product managers have not made things easy. While nearly all the above headphones come in just one version, the DT 770 can be had in no less than 7 current versions:

And to make it more confusing, the “Edition” versions are also randomly called “Premium” or simply “DT 770”. And, from what I gather, still different DT 770 versions were previously offered. Choice is good, but Beyer might have gone too far.

WHAT’S THE DIFFERENCE (revised 4/9)? BIG DISCLAIMER HERE… I’ve only heard the DT 770 Pro 80 personally. But here’s what I’ve been able to figure out from the Beyer website, other reviews, etc:

The Pro versions use a cheaper looking plastic ear cup, have slightly more clamping pressure, and are made to be more rugged. The street price on the home/premium/edition series are at least $50 more. The “Manufactur” version is a custom factory order program from Beyerdynamic. You can pick options, colors, etc. and in a month or two have exactly the headphones you want. Well, perhaps not exactly, as they don’t offer the 80 ohm version for the Manufactur program. There are four different impedances available and, while I’ve only heard the 80 ohm Pro version, here’s my best guess at some of the differences:

32 Ohm – Designed for use with portable gear like an iPod. They supposedly sound similar to, but not as refined as the 80 ohm version reviewed here.

80 Ohm – The apparent favorite among people who like more bass in their headphones. They’re only available in the pro versions.

250 Ohm – In the pro version, these have a coiled cord and Beyer says they’re intended for mixing music. Reviews and published measurements indicate they have less bass than the 80 ohm and 32 ohm versions. They’re best used with a source intended to drive high impedance headphones.

600 Ohm – These are only available in the home version and, based on published frequency response measurements, have much less bass than the other versions. They’re intended for use with a dedicated headphone amp or other source that can handle their unusually high impedance.

WHICH ONE IS BEST? I chose the Pro 80 for several reasons:

They’re what the store stocked, and hence what I listened to

I prefer a straight cable (the Pro 250 uses a coiled cable)

They’re still (barely) usable with portable gear (the 250 and 600 are not)

Beyer doesn’t make the home “Edition/Premium” version in 80 ohm

They’re $50+ cheaper and more rugged than the home “Edition/Premium” versions

But your needs might be different. If you like to crank it up and want to use an iPod or other portable, the 32 ohm Edition is the best choice. If you don’t like as much bass emphasis and have a good source that can handle high impedances, the Edition 600 would be a better choice.

THE CABLE: The 80 ohm versions have a fairly heavy duty and very long 3 meter cable (about 10 feet) wired to the left ear cup. That generous length is good if you like to wander around while wearing headphones, or bad if you have to find something to do with the excess. The 250 ohm version has a coiled cord that supposedly extends to the same length. I personally don’t like coiled cords as they tend to weigh more, pull on your head and are more microphonic (rub against things and create unwanted noises in the headphones). Because the straight cable is very slick and smooth the microphonics are fairly low. There’s a 3.5mm mini plug with a screw on 1/4” adapter. The strain reliefs at both the plug and headphones are very robust and well designed. I’m guessing the cable will last a long time which is a good thing as it doesn’t unplug from the ear cup. This is the sort of cable you can run over with your office chair multiple times and not hurt it.

CONSTRUCTION: The black steel head band seems very tough as do the hinges and adjusting clips. The ear pads and headband pad are easily replaceable. Beyer has black velour and black vinyl pads also available and you can find third party ear pads in real leather and with gel instead of foam.

ERGONOMICS & COMFORT: These are seriously comfortable headphones for three reasons. First they don’t suffer from the dreaded “Shallow Ear Cup Syndrome” like many of their peers. There’s actually room for a human size ear inside (see the pic further down). They’re also fairly light at only about 9 ounces. By comparison the Denon AH-D2000 is about 13 ounces. The ear cushions are covered with a soft velour that adds to the comfort as, unlike vinyl, there’s no sweat build up. While the Pro versions supposedly exert about one third more “clamping pressure” they still sit relatively lightly on your head—especially compared to the Sennheiser HD280. And if you want lighter still, you can bend the steel headband as desired. Finally the bottom of the headband is well padded with soft padding. So unlike say several models (AKG comes to mind), there are no pressure points on the top of your head. The only obvious downside is they don’t fold up for travel, and if you’re a DJ, you can’t swivel the earcups to use one at a time.

SOUND QUALITY (revised 4/23): After 48 hours of continuous break in (like breaking in a pair of new shoes it can, in theory, make a difference due to the initial stiffness of the moving diaphragms), I listened to the DT 770s mostly using a Benchmark DAC1 Pre as the source with a variety of material sourced from my PC and a Slim Devices Transporter. I also used an iPod Touch 3G and experimented with the output impedance on the DAC1. See the Tech Section for more. I compared the Beyer’s to three other popular closed back headphones--the Sennheiser HD280, Denon AH-D2000 and Audio-Technical ATH-M50. I also compared them to my Sennheiser HD590 open back headphones. I only had the ATH-M50s a short time so I had less experience with those.

TWO CAMPS: There are two fairly distinct groups of headphone users. A lot of people, especially those using portable players, are used to an “enhanced” sound with emphasized bass and highs. Many manufactures create a “V” shaped frequency response that’s lowest in the middle and rises strongly at both ends of the spectrum. When you select the “Rock” or “Pop” EQ preset on many portable players, you get just such a “V” shape. If that’s what you’re used to, accurate (i.e. relatively “flat”) headphones can sound boring—at least at first. So most portable players, iPods included, come with headphones with at least a somewhat “V shaped” response. But another group of listeners prefers more accuracy. More accurate headphones tend to be much less fatiguing over time and more natural. Plus, you can always add EQ to punch up the bass and/or highs if you want. Headphone manufactures are put in the difficult position of either offering different models to appeal to the different camps, or trying to compromise with a sound that tries to please both groups.

BEYER’s COMPROMISE? The DT 770 is allegedly for professional studio use and one might expect them to be relatively accurate. But I think Beyerdynamic recognizes many musicians, like much of the public, have come to expect enhanced bass and highs. Musicians buy iPods too. So it’s my guess they tweaked the 770 to appeal more to the tastes of pop/rock musicians while still trying to keep them accurate enough to allow use by recording engineers, etc. Sometimes compromise is a good solution, and sometimes it messes up a good thing.

BASS PERFORMANCE (low impedance source): Let’s say you take your boss to lunch in your polite four door sedan. Driving gently, there’s only muted burble from the exhaust hinting the car isn’t your mother’s Camry. Little does your boss know it has 370 horsepower and could pin him in his seat if you wanted to indulge your inner child with your right foot. That’s kind of how the bass is with the Beyers. Listening to a polite string quartet, there’s only a slight hint of the 770’s reputation for being “bass heavy” but play a hip hop track and hang onto your teeth. It’s Jekyll and Hyde. The Beyers have, by far, the most deep bass of all five cans I compared. In overall bass level with pop music, the rank is roughly DT770 > HD280 > ATH-M50 > D2000 > HD590. But that’s a bit misleading as the DT770, for example, has less upper bass than the say the HD280. The HD280 makes that string quartet sound thick and muddy. The 770 has a very “punchy” bass that only really calls attention to itself when there’s significant deep bass in the music. Male vocals, for example, remain relatively accurate. The overall quality of the bass is better than I expected but it turns out that’s partly related to what they’re connected to.

BASS PART TWO (high impedance source): Based on what I’d read, I expected the bass of the DT 770 to be less controlled than it is. I wrote an article about how source impedance interacts with headphones to change their bass performance and wondered how the 770’s performance would change using a higher impedance source? The answer is quite a bit! Using one standard of 120 ohms, the formerly tight punchy bass of the 770 became more bloated and warm with less deep bass extension. The bass peak now reached up high enough to make male vocals sound thick. In short, the really deep rattle your teeth performance was diminished and replaced by a much less pleasant “boomy” bass peak. I wonder how many who dislike the 770’s bass heard them from a higher impedance source?

MIDRANGE (revised 4/23): The midrange of the DT770, like most closed cans, suffers a little. It’s a bit recessed and sounds a kind of “nasal” on some recordings. But these complaints are relative. The midrange is far more pleasant than the HD280 for example. The M50 sounds warmer (some might say too warm) through the midrange and the $350 Denons still have the best midrange of any closed cans I’ve heard. But the 770’s more laid back mids can sometimes be a benefit on poorly recorded, mastered, and/or ripped material. They’re less “in your face” than the more forward sounding Denons and hence are more forgiving. I rather like the 770’s midrange on a lot of male vocals while on female vocals they sound a bit “dark”. The midrange is somewhat similar to the open HD590 which is also a bit recessed (and some would say “dark”). If you’re a stickler for accurate midrange, I’d suggest the D2000s (or perhaps one of the other Denon models, Shure SRH 840, etc.).

HIGH FREQUENCIES: The 770’s highs are not as bright, revealing, or accurate as the more expensive Denon's. They’re closer to the M50s but the highs have a slight “enhanced edge” to them--not in a harsh way. It’s more an “artificial” sort of enhancement. To use a visual analogy, if you’ve ever seen an over sharpened video or picture, that’s similar to what I’m talking about. Initially it’s impressive, but over time, you realize it’s partly fake detail. The trick worked well enough to get me to take them home from the store. The 770’s highs, despite the “edge”, are still more forgiving of poor source material than the Denon's. And the 770’s highs sound better than the HD280’s. So pick your poison.

SOUNDSTAGE: To my surprise, the Beyers are far more open than the Denons. They also easily beat the M50 and HD280. The Beyer soundstage is deeper and wider and there’s more space between instruments--more like the open backed HD590. More of the ambience comes through. It’s another reason they initially impressed me.

EFFICIENCY (sensitivity): The DT 770s were the least efficient of the five headphones by several dB followed by the HD590s. The other three (Denon, M50 and HD280) were within a few dB of each other at the same volume setting.

PORTABLE COMPATIBILITY: With my iPod Touch 3G, the Beyers sound good on typical heavily compressed pop material but won’t get uber-loud. On really dynamic material, such as Flim & The BB’s Tricycle, the iPod (with its 7 ohm output impedance) clearly lacked bass punch compared to the Benchmark as the bass notes were clipped by the player at higher volumes. The Sansa Clip+ and Fuze did marginally better than the iPod but still fell short. Any portable device conforming to the new EU hearing protection regulations would be seriously underpowered. You can take these headphones with you (if you have room) and they’ll work OK from some portables. But to hear what they can really do, you need a low impedance source with enough beans. See the Tech Section for more details. The 32 ohm version of the 770 would be a much better match for portable use.

MAX SPL: The 770 will play cleanly well into hearing damage levels. If you feed them large amounts of deep bass at high levels, you’ll hear some audible distortion as the drivers run out of excursion (approach their limits of travel). You also get significant intermodulation distortion. This is true to varying degrees for nearly all dynamic headphones but the Beyers are perhaps a bit worse than average in their price class.

SOURCE MATERIAL: The DT 770 is more revealing than the HD280 but less so than the D2000. They’re similar to the M50. If you take them for a test drive I’d suggest using a wide variety of material and not just well recorded audiophile demo stuff. The highs, in particular, don’t get along with some source material.

OVERALL SOUND (updated 4/23): The nearly twice as expensive Denons are much more accurate than the 770s and still the best sounding closed cans I’ve heard on good source material. But the Denons ruthlessly reveal flaws and have a more “in your face” sound. The Beyers sit you a few rows further back in the venue, are more spacious, and try to offer some of the bass and treble “enhancement” many have grown used to. Some are likely to enjoy the punchy deep bass and enhanced highs. The 770's extra bass, at least driven from the Benchmark DAC1, doesn’t get in the way as often as I expected. But those who seek accuracy may find it excessive. The rest of the tonal balance isn’t perfect but, among closed comfortable cans, they’re better than average. The 770s, for example, blow away the well regarded HD280s in virtually every way. So if you like the HD280s, you’ll probably love the 770s.

THE GOOD:

Very comfortable with room for an actual human ear inside

Spacious, engaging sound that’s “enhanced” in ways some might like

Serious deep bass without a lot of “muddy boom”

Laid back midrange is more forgiving on poor source material

Closed back to not disturb others and increase isolation

Solid rugged design

80 ohm impedance allows some portable use at lower volumes

THE BAD:

Too much deep bass for those who prefer more accuracy

Boomy bass with high impedance sources

Midrange too laid back for some tastes

Somewhat uneven highs create a fake sense of detail

Plastic ear cups look kind of low-rent

Not the best match for some portable gear for louder levels

BOTTOM LINE: There are not many closed can I can wear for hours on end. The Denons flunk that test where the DT 770s pass it with comfy flying colors. And they’re also more forgiving of poor source material than the Denons. They sound similar to the Audio-Technica M50s but are much more comfortable. They’re well made and better than the HD280s in every way (except portability). With a low impedance source, the solid, deep, punchy bass can be fun with the right music. And some should enjoy the recessed midrange and “enhanced” highs. Beyer did a reasonably good job of trying to keep them from sounding “too boring” for those who are used to enhanced bass and highs. And they did it in a way that still leaves most of the frequency spectrum relatively unscathed. Some might find the DT 770 a perfect compromise but those seeking serious accuracy should look elsewhere.

TECH SECTION:

OBJECTIVE MEASUREMENTS: I’m big on hard numbers, but I don’t have a HATS (Head And Torso Simulator) or even a fake head with an embedded instrumentation grade microphone. So it would be difficult to make meaningful frequency response, distortion, etc. measurements as I would probably have a hard time even reproducing my own measurements let alone comparing those made by others. Headphones (along with speakers) vary widely in sound and the desired frequency response tends to be more subjective.

HEADROOM TO THE RESCUE (added 4/14): Being unable to make my own measurements, the best ones I know of are at HeadRoom. Here are 4 of the headphones discussed in this review:

The HD280 has an upper bass dip where the others are flat or have a rise. And the M50 and D2000 have similar bass performance. If you scroll down within the comparison window, you can also view distortion, impedance, isolation and the square wave response. The HD280 has a severe dip in the extreme highs. But, otherwise, the four headphones are more similar than different. The Denons are the flattest overall. Looking at the 50 hz square wave response, the DT770s are the winner:

The “flatter tops” (in blue) of the DT 770 square wave response indicates flatter low frequency response than the M50 or Denon. And, while to many ears, the 770s have exaggerated bass, to the microphone, the bass is more accurate than the other three.

It’s worth noting not everyone’s head and ears are shaped the same as the artificial one used by HeadRoom. And that will change the results. And everyone has their own preferences and hears things differently. But the artificial head, microphone, and test gear at least attempt to provide a fair comparison between headphones. Assuming the measurements were made correctly it’s safe to assume, for example, the DT770 and HD280 have more bass than the other two based on the measurements. And indeed that’s what I heard and most others are likely to hear. So there is some valid correlation. But the graphs alone can’t always tell you which one will sound the best.

HEADPHONE IMPEDANCE: The DT 770 Pro 80 is rated at 80 ohms and measured somewhat above that. At the lowest point they’re about 83 ohms with a bass resonance peak (in free air, not on a head) at about 50 hz and nearly 110 ohms. They also exhibit the typical rise at the high end due to voice coil inductance. The phase shift (in white) is very linear and gradual making them an easy load:

IMPEDANCE INTERACTION: As discussed in the subjective review, the Beyer’s bass was well controlled when driven from the near zero ohm output of the Benchmark DAC1 Pre. The IEC standard from 1996 (before portable digital players became seriously popular) specified a 120 ohm output impedance. I put 120 ohms in series with the DT 770s on the Benchmark and the sound changed significantly. 120 ohms is enough to seriously degrade the electrical damping of the driver which raises the Q. That, in turn, causes the bass to peak more, at a higher frequency and roll off sooner (less deep bass). The bass also ends up less damped overall and hence less controlled and less “tight”. That’s exactly what I heard. The bass got more muddy, boomy and didn’t reach as low. This is discussed further in the Impedance Article.

The 120 ohm source also creates a frequency response error in the signal driving the headphones. Here’s the signal from the Benchmark at zero ohms in blue, and from a 120 ohm source in yellow. There’s almost 1.5 dB of variation. Note this is the electrical input level, not the acoustic output of the headphones but it will still cause a similar response variation in the acoustic output compared to a zero ohm source (in addition the the headphone’s regular response variations):

SOURCE IMPEDANCE SUGGESTIONS: If you’re not a fan of bloated bass, the lower the output impedance the better with the Beyer’s. This increases the electrical damping and tames their bass boost. When I tried them with my iPod Touch 3G, which is around 7 ohms, the bass lost some punch (also possibly due to the peaks being clipped). And it gets worse as you go up in impedance from there.

SOURCE DRIVE LEVEL: On highly compressed pop music I cranked up the Beyer’s to about as loud as I would normally go and measured the signal on a scope while listening. The peaks were hitting +/- 400 mV which is only about 280 mV RMS. Even most portable devices can manage that. But, playing material with a wider dynamic range at loud levels, I needed up to 3.5 volts peak-to-peak which is about 1.2 volts RMS. The $20 FiiO E5 can manage about 1.3 volts RMS and it got plenty loud even on highly dynamic material but the Beyer’s likely deserve better than the E5.

To translate this into power output, at a more-than-needed 1.5 volts RMS, that’s 70 mW into 32 ohms, 28 mW into 80 ohms, and 9 mW into 250 ohms. Sources rated somewhere in that range should have enough cajones to do the job without clipping or running out of gain.

POWER HANDLING: Beyer rates the 770 Pro at 100 mW. For the 80 ohm version, that’s 2.8 volts RMS and would be uber-loud. The driver, however, runs out of excursion well before that at low frequencies.

SOURCE QUALITY: As mentioned in the review, while not the most revealing cans on the planet, the Beyer’s are well above average. So poor quality sources, poor recordings, lower bit rate MP3’s, poorly designed amps/DACs, etc. are revealed for what they are. The Beyer’s sometimes take a bit of the edge off, but they don’t “gloss over” defects the way a lot cheaper headphones do.

TECH SUMMARY: There were no real technical surprises except I wonder how much of the 770 Pro 80’s reputation for unpleasant bass is from people using higher impedance sources?